In the context of the present invention, the term organopolysiloxanes is intended to include dimeric, oligomeric and polymeric siloxanes.
The use of dialkyltin(IV) compounds as condensation catalysts in RTV-1- and RTV-2-silicone rubbers is generally known. However, in RTV-1-alkoxy compositions these tin compounds have the disadvantage that they also catalyze the unwanted cleavage of the siloxane chains by alcohol radicals, i.e. "equilibration", whereupon alkoxy end groups on the polysiloxane chain which are no longer capable of crosslinking are formed, and adequate crosslinking of the composition is therefore no longer possible: i.e. no adequately stable vulcanization product is obtained when the composition is used for the intended purpose. The storage stability, stated as the period of time which the RTV-1-alkoxy composition can be stored without noticeably losing its commercially acceptable properties, is drastically reduced by equilibration.
Known methods for prolonging the storage stability include:
The replacement of the tin catalyst by a titanium or aluminum chelated catalyst, for example as disclosed in U.S. Pat. No. 3,334,067. The disadvantage here is the yellow coloration of the compositions, as a result of which only opaque but no transluscent compositions are possible. PA1 The replacement of the tin catalyst by a titanium catalyst of the general formula Ti(OR).sub.4, for example, as disclosed in EP-A-747 443, with the disadvantage that only siloxanes which contain no silanol groups can be processed. The use of adhesion promoters with such catalysts is limited because of adverse effects on t he activity of the catalyst. PA1 Reduction in the amount of the tin catalyst, with the disadvantage of a very slow vulcanization. PA1 The use of less aggressive tin catalysts, for example tin chelated catalysts, for example as disclosed in U.S. Pat. No. 4,517,337. An excess of chelating compound such as acetylacetonate, is necessary. However, this chelating agent is volatile, toxicologically unacceptable, a health hazard, and can also lead to yellowing of the vulcanization product. PA1 The addition of alcohol-trapping agents, scavengers which react with alcohols on the basis of their high reactivity, for example as disclosed in U.S. No. 4,417,042. However, the addition of such scavengers is not only expensive, but also impairs adhesion properties. PA1 R.sup..alpha. and R.sup..beta. are hydrogen or a monovalent C.sub.1 -C.sub.10 -hydrocarbon radical optionally substituted by hydroxyl, fluorine, chlorine, bromine, C.sub.1 -C.sub.10 -alkoxyalkyl or cyano groups, PA1 u is from 1 to 6 and PA1 v is from 3 to 100, PA1 a is 1 or 2, PA1 R.sup.1 and R.sup.2 are independently hydrogen, methyl, or hydroxyl radicals, b and d are 2or 3, PA1 c is from 2 to 15, PA1 e is 0 or 1, PA1 L is a radical from the group consisting of --O--, --COO--, --OOC--, --CONR.sup.3 --, --NR.sup.4 CO--and --CO--, PA1 R.sup.3 and R.sup.4 independently are hydrogen or, C.sub.1 -C.sub.10 -alkyl radical(s), and PA1 M is a monovalent C.sub.1 - to C.sub.20 -hydrocarbon radical which is optionally substituted by hydroxyl, fluorine, chlorine, bromine, C.sub.1 -C.sub.10 -alkoxyalkyl or cyano groups, PA1 R.sup..alpha. and R.sup..beta. are a hydrogen radical or a monovalent unsubstituted hydrocarbon radical, in particular hydrogen or C.sub.1 -C.sub.3 -alkyl radicals, such as the methyl or ethyl radical; PA1 u is an integer from 1 to 4, in particular 2 or 3; and PA1 v is an integer from 3 to 25, in particular from 5 to 10. PA1 R' and R" are C.sub.6 -C.sub.30 -alkyl radicals, PA1 Y is a divalent polyether unit of the general formula (I), PA1 X is Na or K and PA1 Ar are C.sub.6 -C.sub.30 -aryl radicals or C.sub.7 -C.sub.30 -aralkyl radicals. PA1 (A) organopolysiloxane(s) with terminal alkoxy groups and PA1 (B) alkoxysilane(s) which contain at least three alkoxy groups, and/or partial hydrolysis products thereof. PA1 R, R.sup.5 and R.sub.6 are each independently monovalent C.sub.1 -C.sub.8 -hydrocarbon radicals, optionally substituted by fluorine, chlorine, bromine, C.sub.1 -C.sub.4 -alkoxyalkyl or cyano groups, PA1 f is 0 or 1 and PA1 g is a value which corresponds to a viscosity of the organopolysiloxane (A) of from 0.05 to 1000 Pa.multidot.s. PA1 R.sup.9 and R.sup.10 have the meanings of R and PA1 h is a value which corresponds to a viscosity of the dimethylpolysiloxane of from 10 to 500 mPa.multidot.s. PA1 Z has the meanings NH.sub.2, NH-CH.sub.2 CH.sub.2 NH.sub.2, NHR, and glycidoxy, and PA1 R.sup.11 has the meaning of R.